The purpose of this grant is to obtain a general purpose Philips CM 10 transmission electron microscope. This is a "user friendly" instrument that is microprocessor controlled and is well-suited to the multiple needs of a diverse NIH-funded user group. The School of Medicine is a new developing institution that has experienced an explosion in the level of NIH research funding during the past five years. Maintaining this momentum is critically dependent on the acquisition of technology essential to existing and planned research activities. Our present microscope is a 16-year-old Hitachi 125-E. This is the only functioning TEM in both the School of Medicine and the University of Nevada. This instrument has been under service contract until 1985. A service contract is no longer possible because parts are not available or are difficult to locate. Thus, we are faced with the imminent loss of all TEM capability at the School of Medicine. This will have an immediate impact on existing NIH-funded projects that are critically dependent on TEM, and initiation of new directions that require TEM has become impossible. The current status of TEM facility has had an obvious impact on recruitment of new senior NIH-funded faculty who utilize TEM in their research The user group represents diverse research interests that include the ultrastructural location of opsonic proteins in microbial capsules (Kozel), electrophysiology and cell-to-cell coupling in the GI system (Rogers, Pubicover, and Sanders), molecular biology of Cytomegaloviruses (St Jeor), hormone-receptor interactions with intracellular proteins (Buxton), and the lethal mechanism of natural killer cells (Hudig). The specific applications of TEM are diverse, but the basic need for routine availability of TEM services is common to all users. As a consequence, the requested instrument will be a core facility designed to function as a service to the user group. The administration of the School of Medicine has commited the necessary resources to maintain a service contract on the instrument for its useable life and to employ a full time technician to maintain the instrument and provide TEM services for the NIH-funded user group.